I'm not sure if it is seeing a comeback, but back in the days of Telepersonals/Casual Encounters and the (similar) website (which name I forget atm) I banged LOTS of guys wives in front of them.
The typical dynamic was the guy usually had a wife that was out of his league and really got off on the fact that HE got to marry and fuck such a hot woman anytime he wanted... and liked the affirmation and validation that other guys fucking his wife provided. Often the woman had a really high sex drive and the husband couldn't keep up. I don't think any guy could keep up with some of these nymphos. Also, since men are so visually aroused, watchign live porn with a woman he already thinks is hot, is exciting to them.
Many of them were swingers, or wannabe swingers.
I was pretty careful to screen and look out for any instability in either of them, as I didn't want to end up getting beat up or killed of something. Never had any problems.
Worst/weirdest experience was this one couple I met up with at a downtown bar and went back to their Avenue Rd townhouse. Their desired scene was to have her lift her skirt and I fucked her fron the front while standing and he fucked her from behind in her ass. He was all enthused and horned up, happy etc. I slipped in and started fucking her and he was jacking himself to get hard, then slipped it in her ass... and came within about 10 seconds.. She was just getting started and I was still some time away from coming and he went Jekyll and Hyde and told me to stop fucking his wife. She said,
'no honey, I'm enjoying this, let us keep going for a bit more'. He said nothing for about a minute while I was trying to concentrate on blowing my nut before he changed his mind again. then he yelled to stop fucking his wife. I stopped. She sort of said WTF to him and he started being an asshole. I quickly pulled my pants up and left.

But that's about it for bad experiences.
Otherwise I probably did the hotwife and/or cuckolding scenario with married couples about 15 times over the years. More if I count swinging.
Every one was attractive to hot. I became friends with many of the couples and hung out socially too.
Having said all that, one fantasy that I want to live out it is like those Russian SellYourGF pornos. Where the young guy agrees to let his friend or older guy to fuck his gf for cash. She reluctantly agrees, and then really gets into it... and he sits nearby, pissed but passive.
Weirdly, I'd even be turned on by a plain Jane girlfriend type, doesn't have to be super hot.
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